Choosing the Right EMC Test Lab

Would you choose a brain surgeon from the phone book? Probably not. You would more likely ask your doctor, friends, and relatives for recommendations. And after you did find someone, even if you were favorably impressed by reputation and apparent competence, you still would make sure he had experience treating your type of problem.

So it is with choosing an EMC test lab for full compliance testing. Many labs rate word of mouth as their primary source of new customers. Advertising, trade exhibitions, web sites, newsletters, and publication of staff-written articles all are important, but recommendations from satisfied customers have the most impact.

The process of deciding which lab to use comprises a number of stages, starting with the clarification of your requirements. To help organize your needs, consider the services that labs offer as well as how they promote themselves.

Accreditation and CE Marking

Like most areas of specialization, EMC testing has its own list of agencies, acronyms, and abbreviations. These are some of the terms used in relation to a lab’s accreditation and CE Marking capabilities.

A2LA—American Association for Laboratory Accreditation

ACB—Association of Competent Bodies

CAB—Conformity Assessment Body

CE—Conformité Européenne

DoC—Declaration of Conformity

EN—European Norm

FCC—Federal Communications Commission

MRA—Mutual Recognition Agreement

NARTE—National Association of Radio and Telecommunications Engineers

NEMKO—Norges Elektriske Materiell Kontrol – Norway

NIST—National Institute of Standards and Technology

NVLAP—National Voluntary Laboratory Accreditation Program

VCCI—Voluntary Control Council for Interference – Japan

In the United States, lab accreditation is performed by the A2LA or NVLAP according to programs established by NIST. MRAs are intended to allow U.S. companies to have their products CE marked before being exported, and they also will allow European manufacturers to meet FCC regulations in their country’s labs.1

Many labs consider their certification and accreditation to be strong competitive advantages. For example, literature from EMC-Turntech stated that it is a fully accredited laboratory that meets the requirements of the EN 45001 for the CE Mark, the FCC NVLAP for DoC Approvals, and Japan’s and Taiwan’s lab registration processes for VCCI and BCIQ Approvals. Through an MRA, it is qualified for Australia and New Zealand’s EMC Framework AS/NZS.

Although most labs will make similar claims, if you plan to export your product, it will have to be tested to the relevant standards. The lab you choose must be qualified to run the specific tests you will require.

Other than actual radio transmitters which can only be approved after EC type-examination, you have two ways to obtain the CE Marking. The internal control of the production procedure can be used in cases where harmonized standards (EN xxxxx) are available and applied. Alternatively, a technical construction file can be used in cases where standards are not available or not applicable.

In any case, you must prepare a declaration of conformity stating that you have met all the conditions of the EMC Directive. Compiling a technical file will help you to demonstrate later that the DoC is well founded should you need to.

In following the internal production control procedure, the manufacturer assesses both the design and production of products. Testing must form a part of this procedure. A model of the DoC is described in standard EN 45014, General Criteria for Supplier’s Declaration of Conformity.

If you follow the technical construction file approach, your product must be tested and approved by a Competent Body. A Competent Body is similar to an accredited lab, but it also can certify tested products which an accredited lab that is not a Competent Body cannot do. Technical data issued by the manufacturer such as schematics and test results, is assessed by the Competent Body. Test results may be from the manufacturer’s own tests, or they also may include measurements from an accredited lab.

The approach you follow depends upon your circumstances, but KCS Certification recommends that the technical construction file be retained for at least 10 years after production of the product has ceased.2

The KCS Certification Guide also describes organization of a technical file in two parts. The first part should contain a list of the essential information necessary for the conformity assessment inspection:

Name and address of the manufacturer and the type designation of the product.

A list of the EN standards applied by the manufacturer and the solutions adopted to satisfy the essential requirements.

A description of the product.

The product manual where applicable.

A general drawing of the product.

Records of complaints regarding the certified product.

The second part must consist of the test reports, information on the quality manual, plans, descriptions of the products and processes, and applied standards.2

Physical Considerations

A product’s size, weight, power requirements, and civilian or military use all affect its testing. For example, it makes a difference whether the product is an electronic subassembly for a car or a complete vehicle. Obviously, testing a complete vehicle requires a large site, good access, and a heavy-duty turntable.

As an example of a test site targeted at large objects, EMCC DR. RAŠEK

has built a 40-m open air test site (OATS) in Ebermannstadt, Germany. Figure 1 shows the pyramidal wooden structure that forms the roof and walls, and there is a 4-m × 3-m door as well as a hydraulic underfloor elevator. The ground plane is designed for machine and vehicle loads up to 75 tons.

Car companies have their own EMC labs which they use to test your vehicle-related product. Before you deliver a product at the completion of a project, it makes sense to have it tested first by an independent lab. There are labs near Detroit with test areas correlated to car-company test facilities. Similarly, if you are working on a military project, many labs specialize in testing to MIL standards and are familiar with the necessary report formats.

Don’t overlook the power requirements of your product. A large, three-phase machine, especially one requiring 50 Hz for the European market, will restrict your choice of labs. Of course, your selections are limited anyway unless you intend to transport a large machine a long distance.

You may have more than just an EMC requirement to satisfy. Mike Violette, president of Washington Laboratories, described a particularly interesting recent job.

“We required the combination of an EMC, an electrical safety, and a machinery and vehicular certification team to assess the CE Marking aspects of a mobile building machine. This unit forms rolls of steel into arched panels on-site for use in Quonset-hut structures,” he explained. “The machine included a diesel motor for hydraulic presses and material handling, electronic computerized controls, and an electric generator and ancillary equipment for building insulation, all on an on-road trailer vehicle.”

Responsibilities

Your own experience and competency also are major criteria affecting your choice of an EMC lab. When several labs were asked what they thought of customers’ expectations, their responses ranged from uncertain to realistic.

Certainly, if it is the first time you have used a lab, you may not know what to expect. It is reasonable to rely on a test lab for guidance with regard to the areas of compliance on which you should focus. The lab can provide guidance, perform the tests, and offer suggestions about design changes if the product fails the tests. On the other hand, it is solely the manufacturer’s responsibility to meet the relevant standards.

The extent to which compliance is the manufacturer’s responsibility is highlighted in a description of tests on a Sandia National Laboratories project (Figure 2). Scott Proffitt, director of sales and marketing at U.S. Technologies, explained, “The EUT was a tester for a high-voltage current switch component. An idea of the size and complexity of the job can be realized from the ESD procedures. More than 18,000 static discharges were required for 79 discharge points. This included several voltage levels, multiple discharges to each point, and air, contact, and vertical coupling plane discharges. The three main components of the system—a PC controller, a 7-ft tall, fully loaded 19” rack, and an 8 ft3 environmental test chamber—weighed about 1,200 lb.

“Failure of a few of the CE-marked system subcomponents during immunity testing particularly interested our staff,” he continued. “These failures were not at all related to the interfacing with the Sandia portions of the product.” Nevertheless, it was Sandia’s responsibility to do whatever was needed to pass the tests successfully.

Precompliance Testing

A good way to enhance your product’s chances of passing compliance testing on the first try is to perform precompliance testing. Precompliance activities vary, but Amplifier Research defined it as any EMC test that is conducted in-house before submitting products to a certified EMC test lab for full compliance testing.3 Many labs also offer precompliance testing, so the question of where the work is done and who does it is a matter of cost, convenience, and competence.

The tests are conducted to gain an understanding of how the EUT is likely to perform in the full compliance test, but precompliance tests generally do not exactly follow the requirements spelled out in the pertinent EU standards. An example is the use of a field probe to provide feedback to control leveling of the E-field in a shielded room. The relevant test actually may call for use of the substitution method.

Mr. Proffitt of U.S. Technologies pointed out, “Manufacturers are doing more precompliance testing than ever before. Whether done at their own location or at our facility, precompliance testing saves a great deal of time, money, and headaches in the end. Occasionally, we still see a manufacturer that has completed product development only to find that major changes are needed for compliance.”

The level of precompliance testing being done by U.S. Technologies’ clients is exceptional judged by responses from many other labs. One lab commented that the few customers who did perform precompliance tests were capable of doing this work either because they had personnel with previous compliance testing experience or they had sufficient volume of new products to justify the purchase of precompliance testing equipment.

In another case, Robert Martin, engineering manager of the Intertek Testing Services ETL SEMKO Division, said, “Only about 10% of our clients conduct any pretesting at their own facilities to uncover potential noncompliance issues before submission. Approximately 20% of our clients conduct diagnostic testing prior to submitting a final sample. More than half of our clients need education on the standards and tests their products will be subjected to.”

A report on the 1998 activities of Reg TP (The Regulatory Authority for Telecommunications and Post in Germany) stated that 45,000 items of equipment were checked, and deficiencies were found in 6.5% of the cases. The report concluded that “…many manufacturers of electrical and electronic products do not pay enough attention to EMC. It is strongly recommended that manufacturers invest more in EMC testing.”4

Amplifier Research offers five reasons why precompliance testing is both an immediate and an on-going benefit:

Cost Savings

In-house testing reduces the total test time required at a certified test lab. With fees of $1,000 per day or more, significant savings can be realized by precompliance testing. Major EMC problems can be identified and corrected before the product is submitted to the test lab for full compliance testing.

Reduced Time to Market

Since many manufacturers do not consider EMC in their product development, they are unprepared for the delays encountered at the test lab. In addition to the normal delays, there may be rescheduling delays to deal with when a product fails.

A failure may require anything from a minor tweak to a complete board redesign. Often, the nature of the failure is such that little or no information is available to pinpoint the problem and facilitate a quick fix. After modifications have been implemented, the process begins again. This iterative process often can be very time-consuming and expensive.

Improved EMC Performance

Ongoing precompliance testing conducted at the component or board level during the design process results in products that are inherently EMC compliant. Products exhibit a much lower failure rate at the test lab, and the time from product conception to product introduction is reduced significantly.

In-House EMC Expertise

A precompliance test system provides the tools required not only to engineer EMC compliant products, but also to fix those products that fail at the test lab. The engineers and technicians that use the system develop an understanding of EMC fundamentals that can be transferred across all product lines.

Quality Assurance

Precompliance testing can assure product conformity over time. This is especially important when changes in major components are required. Also, the ability to determine the threshold at which products experience EMC failures results in higher-quality, more immune products.

Products tested only to spec levels may exhibit problems when exposed to higher fields or, given the uncertainty in EMC testing, may even fail at specified field levels. The result—unsatisfied customers. The capability to test in-house, to threshold, and test beyond the specs often leads to greater customer satisfaction.3

Training and Qualifications

If you feel that you really need some help before you can make a choice of labs or run your own precompliance tests, consider attending a seminar or short course on EMC that several labs conduct periodically. You will learn a great deal, and you will have a reference point against which you can compare other labs.

The IEEE EMC Society sponsors an annual symposium. Specialized training material including the EMC Experiments Manual is available at the symposium or directly from the society’s education committee.

When you do select a lab—perhaps from those listed in EE-Evaluation Engineering’s July, 1999 EMC Buyers’ Guide—make sure to review the professional qualifications of the staff. The lab’s personnel will be performing tests on your product, so it is important that they have the necessary training. In addition to personal engineering and technical degrees, look for NARTE certification as a sign of competence.

After evaluating several organizations, the U.S. Naval Air Command selected NARTE to be the administrative agent for EMC certification. And, the FCC has authorized NARTE to administer examinations for FCC commercial licensure.

References

1. O’Shea, P., “EMI/RFI Test Labs Get Your Products to Market on Time,” EE-Evaluation Engineering, November 1996, pp. 53-59.

Note: This EE-Evaluation Engineering article can be accessed on EE Online at www.evaluationengineering.com. Select EE Article Archives and use the key word search.

2. “Conformity Assessment Procedures Regarding Electromagnetic Compatibility (EMC),” Document KCS/RD_030, Issue 2, KCS Certification, Arnhem, The Netherlands.

3. “EMC Precompliance Testing,” Amplifier Research, Application Note 36.

4. Schreyer, W., “EMC Testing More Important Than Ever,” News from Rohde & Schwarz, number 163, 1999/III, Vol 39, pp. 34, 35.

Acknowledgments

The following companies provided information for this article.

Chomerics/Parker Hannifin (781) 935-4850

Communication Certification Laboratory (CCL) (801) 972-6146

D.L.S. Electronic Systems (847) 537-6400

Elliott Labs (408) 245-7800

EMCC DR. RAŠEK (01149) 9194 9016

Euro EMC Service (01149) 3328 430141

Hermon Laboratories (01197) 2662 88001

Intertek Testing Services (800) 967-5352